Cathode ray oscillograph



Jan. 9, 1934. w. ROGOWSKI ET AL CATHODE RAY OSCILLOGRAPH Filed July 18, 1928 Patented Jan. 9, 1934 UNITED STATES,

CATHODE RAY OSCILLQGRAPH Walter Rogowski'and Eugen Flegler, Aachen, Germany 4 Application July 18, 1928, Serial No. 293,627, and

2 Claims.

This invention relates to cathode ray oscillographs for taking time and instantaneous photographs of repeating .or non-repeating. phenomena.

5 In the use of the cathode ray oscillograph for recording or visualizing oscillations, and more particularly non-repeating oscillations occurring within a very short time, such as for example in one millionth of a second or even in a shorter time, one has to work with a very high intensity of radiation of the cathode ray in order to obtain asuflicient blackening of the photographic plate or a sufliciently strong fluorescence of the screen at thespot where the oscillogram is traced.

In the cathode ray oscillographs known hitherto a considerable amount of the intensity of radiation originally present becomes lost on the path from the cathode to the fluorescent screen or photographic emulsion. As a matter of fact the electrons are emitted from the cathode in the form of a cone, and there may be veryconsiderable stray. In order to prevent an excessively diiluse radiation and obtain a sufliciently sharp oscillogram, it is commonly known to pass the electron stream through the holes of diaphragms arranged between the cathode and the fluorescent screen or photographic plate, but the holes are usually so small that only a moderate fraction of the electrons passes through them. For increasing the intensity of radiation it has been proposed to arrange a concentrating coil between the cathode and anode or between the cathode and diaphragm and to pass through this coil a current of such a strength that the electrons will have their point of concentration exactly on the photographic emulsion or one the fluorescent screen. But with this arrangement a high intensity of radiation can only be attained when the hole in the diaphragm is relatively large. On

the other hand, it is preferable to make the hole of the diaphragm very small in order to prevent excess radiation on the photographic emulsion or on the fluorescent screen. High intensities can still be attained in the recording chamber when the strength of current in the said concentrating coil is chosen so that the point of concentration of the electrons will be situated in the diaphragm hole itself. Practically all electrons emitted by the cathode in the form of a cone will then pass through the hole of the diaphragm into the deflecting and recording chamber, but the electrons will then again diverge conically in the deflecting chamber, the apex of the cone lying in the hole of the diaphragm, and it is impossible to obtain with such an electron ray a clear tracing Germany August 1, 1927 of the oscillogram. It is for this reason that the arrangement of the concentrating coil between the cathode and anode or between the cathode and diaphragm has not yet been used in actual practice.

The present invention has for one of its objects to avoid the said difficulties and to provide a cathode ray oscillograph in which the lastsaid arrangement with a concentrating coil can be used with advantage by providing between the diaphragm and the screen or photographic plate still another concentrating coil by which the electrons are concentrated a second time in the deflecting and recording chamber. With an oscillograph constructed in accordance with the invention the hole ofthe diaphragm can be made as small as desired and the current for the concentrating coil interposed between the cathode and anode or between the cathode and the diaphragm can be chosen so that all electrons emitted by the cathode will flow through'the small hole of the diaphragm. I The current of the second concentrating coil arranged in the deflecting and recording chamber is at the same time chosen so that all electrons proceeding conically from the diaphragm hole are concentrated on the photographic layer or fluorescent screen.

By the arrangement and proper adjustment of the two concentrating coils the highest possible intensity of radiation and sufliciently sharp graphs are attained, also in case non-repeating phenomena of very short duration have to be recorded on the photographic emulsion or made visible on the fluorescent screen. Owing to the small size of the hole of the diaphragm excess radiation is comparatively small. If, however, the exciting voltage must remain cut in for a very long time as is, for example, necessary for recording non-repeating phenomena, such as in lightning and the like investigations, a premature blackening caused by diffuse rays may, in spite of the arrangement just described, make the photographic layer entirely useless for the recording of short-time phenomena, even if the ray is deflected in a well-known manner by electric or. magnetic fields laterally of the photographic layer or fluorescent screen during the 'time in which no recording of oscillations takes ries at least one diaphragm at each of its two no ends and is provided with deflecting fields arranged in such a manner that the cathode rays are entirely confined in the chamber during the time of blocking and that neither the cathode rays themselves, nor diffuse stray rays, nor emanated Rdntgen rays will pass out of the end of the blocking chamber which is directed toward the recording chamber. The photographic layer is therefore protected against any influence of blackening rays until the blocking is released.

The invention finally resides in a method of operating oscillographs of the kind described. For recording instantaneous non-repeating phenomena it is necessary to keep the oscillograph ready for working during a longer period of time and to cause the cathode ray to pass into the de fleeting and recording chamber only in the moment the transient to be recorded occurs. In order to attain this, it is proposed according to the invention that the transient to be recorded on its arrival at the oscillograph does not only initiate the time deflection (sweeping motion) but also causes the release of the blocking of the cathode ray or the cutting in of the exciting voltage. In oscillographs with a constantly applied exciting voltage and blocking of the cathode ray this is performed in a simple manner by branching part of the arriving wave and leading it over a short conductor to a switch mechanism through which it causes the closing of the circuit for the time deflection and the releasing of the ray blocking. The releasemust be accomplished when the main part of the wave reaches the deflecting plates over a longer conductor. In this case the time deflection can be initiated at the same time the blocking is released. The arrangement may also be made so that the transient to be recorded initiates only one of the two operations, which means that it releases for instance the blocking which in its turn initiates the time deflection. In both cases the coupling is effected in the usual way such as galvanically, inductively, capacitively, by spark gaps, electron discharge tubes or the like.

In order to allow of the invention to be more clearly understood two embodiments of the same are illustrated in the accompanying drawing in which:

Fig. 1 is a diagram of a cathode ray oscillograph with two concentrating coils, and

Fig. 2 is a diagram of an oscillograph with two concentrating coils and a cathode ray blocking chamber.

Referring now to Fig. 1 of the drawing, 3 is the cathode, 4 the anode, 5 the diaphragm and 6 a fluorescent screen. Arranged between the cathode 3 and the diaphragm 5 is the first concentrating coil '1 the current of which is chosen so that the cathode rays are concentrated immediately in the hole 5' of the diaphragm 5. As

the cathode rays after passing through the diaphragm hole 5' diverge again, there is arranged between the diaphragm 5 and the fluorescent screen 6 a second concentrating coil 8 which concentrates the cathode rays a second time in such a manner that a sharp spot or trace of light is produced on the screen 6.

The oscillograph shown in Fig. 2 diflers from that according to Fig. 1 in that the diaphragm 5 is replaced by a cathode ray blocking chamber 9 and that it comprises a. Faraday's cage 10 for measuring the electron stream. 'I'he blocking chamber has at one of its ends a diaphragm 11 with a hole 11 and at its other end a diaphragm 12 with a hole 12'. The chamber 9 also con- 2211155 two oppositely disposed deflecting plates With the oscillograph according to Fig. 2, the rays emitted by the cathode 3 after being concentrated by the coil 7 pass through the hole 11' into the blocking chamber 9. In the chamber 9 the electric fields existing between the deflecting plates 14, 15 deflect the ray in such a manner that it is wholly conflned in the chamber and that neither electrons nor emanated Rontgen rays can pass out of the chamber. Only by caus- -15 to disappear the blocking of the cathode ray is released so that the electrons will now pass through the opening 12' and can be used for tracing oscillograms on the screen 6.

The screen 6 may of course be replaced by a photographic plate or film on which to record the phenomena.

Having thus described our invention what we claim as new and desire to secure by Letters Patent, is:-

1. An oscillograph comprising the combination with a cathode for discharging a stream of electrons, an anode and a receiving surface, of an obstructing chamber between the anode and the receiving surface, one diaphragm at each end of the obstructing chamber, an aperture in each diaphragm wherethrough to pass the stream of electrons, and deflecting means in the said chamber for temporarily deflecting the electron stream in the chamber to prevent the stream itself or emanated Riintgen rays from'passing out of the obstructing chamber to the receiving surface.

2. An oscillograph comprising the combination with a cathode for discharging a stream of electrons, an anode and a receiving surface, of a stream obstructing chamber between the anode and the receiving surface having an apertured diaphragm at each of its ends and deflecting means for temporarily deflecting the stream of electrons off the receiving surface, a concen- 2.30 trating coil between the cathode and one end of the obstructing chamber, and another concentrating coil between the other end of the ob- 

